It has been known that a sulfonyl chloride compound represented by the formula (2):
wherein R1 represents a hydrogen atom, a halogen atom, an alkyl group which may be substituted with a halogen atom or atoms, an alkenyl group which may be substituted with a halogen atom or atoms, an alkynyl group which may be substituted with a halogen atom or atoms, an alkoxy group which may be substituted with a halogen atom or atoms, an alkylthio group, an alkylsulfonyl group, an alkoxycarbonyl group, a cyano group, a nitro group, a carbamoyl group, an amino group, an alkylamino group or a dialkylamino group,R2 and R3 are the same or different and each represents a hydrogen atom, a halogen atom or an alkyl group which may be substituted with a halogen atom or atoms, R4 represent a hydrogen atom, a halogen atom, an alkyl group which may be substituted with a halogen atom or atoms, an alkenyl group which may be substituted with a halogen atom or atoms, an alkoxy group which may be substituted with a halogen atom or atoms, an alkylthio group, an alkylsulfonyl group, an alkoxycarbonyl group, a cyano group, a nitro group, a carbamoyl group, an amino group, an alkylamino group or a dialkylamino group, is a useful compound as an intermediate of sulfonylurea herbicides (e.g. U.S. Pat. No. 4,994,571 and U.S. Pat. No. 5,017,212).
As processes for producing thus sulfonyl chloride compound represented by the formula (2), a process comprising reacting the corresponding pyridazine compound with a sulfonating agent followed by reacting with a chlorinating agent has been known (e.g. US 2005-32650 A).